1. Field of Invention
The invention relates to an electric air pump employed for a secondary air supply system, and more particularly, to an electric air pump having a motor with a brush.
2. Description of Related Art
An electric air pump having a motor with a brush is generally employed in a secondary air supply system for purifying the exhaust gas. It is necessary to prevent excessive heating of the brush of the motor for the electric pump so as to avoid the failure in the pump operation caused by the excessive temperature rise in the brush. The publication of JP-A-5-202889 discloses the art for blowing air to the brush so as to be cooled.
In the art disclosed in the publication, the brush is blown by air, but the actual temperature of the brush cannot be estimated. It is difficult to determine whether the temperature of the brush has decreased to the temperature equal to or lower than an allowable value.